Magnetic analysis of drills



Aug. 28, 192& 1,682,435

T. SPOONER MAGNETIC ANALYSIS OF DRILLS Filed Oct. 25, 1921 WRTNESSES: v INVENTOR Thomas 5 0000/.

Patented Aug. 28, 1928.

UNITED STAT- 1,682,435 PATENT"- OFFICE.

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' monn'rrc ANALYSIS on nmns Application filed October 2 5, 1921. Serial 1T0. 510,320.

from a large number of tools, a small number which was tested for hardness and wearing qualities by destructive tests. Based on results of tests on a very-small number of tools, the character of the remaining tools was considered as having been ascertained. This procedure was. very inefiicient in that the results of tests'on certain articles were relied upon to indicate the character" of others not tested;

The present invention has, among its objects. to provide a method of and apparatus for testing machinetools and materials which shall: be. simple and effective, and whereby the character of such tools and materials may be readily ascertained by relatively unskilled workmen.

It is a further object of this invention to serted a resistor 18 adapted to be shortprovide a method of and apparatus for testing which is capable of determining the qualities of materials and tools without destructive tests.

' In practisingmy invention, I provide a magnetic circuit of whicha tool or other article to be tested forms a part and which also contains a standard tool or article of known quality. Magneticfluxes are induced in this circuit and the differences in magnetic characteristics of the two articles is ascertained by reading the deflections on a sensitive movable armature. which is so placed asto be affected by the fluxes in the magnetic circuit. a

In the accompanying drawing constituting apart hereof and in which like reference characters designate like parts,

Fig. 1 is a plan view of an apparatus embodying my invention;

Fig. 2 is a side elevational View thereof,

and

Fig. 3 is a diagrammatic view of my apparatus, showing the electrical connections thereof; f

The apparatus comprises a base 1, usually of any suitable insulating material, that has secured thereto a pair of ydkes and 3, generally consisting of softiron 'orsteel of high permeability. Alined openings 4 are v formed in oppositeends of ,yokes 2 and 3,

able manner.

a plug'5 is placed'in one end of one of the openings 4 in yoke 2*and another plug 5 placed in a diagonally opposite opening 4 in yoke 3. Projecting portions or pole pieces 6 are formed centrally. of yokesv 2 and 3 to extend inwardly and embrace the movable armature 7 which has a pointer 8 secured to the moving coil thereof to. move over a. scale 9 secured to base 1 in any suit- Coils' 10 and 11 are placedwithin the ends of yokes 2 and 3 and are secured in position by straps 12. Openings 4' in said coils are so formed that they aline with openings 4 of the yokes; The yokes are split horizontally, as shown at 13, Fig. 2, and articles or'materials 14 and 15 to be tested are in serted in alined openings 4, screws 16 being provided to securely clamp said articles in position on the apparatus. Coils 10 and 11 are connected in series by conductors 17 which also connect said coils to two pairs of poles of a three-pole double-throw reversing switch 20. In the circuit 17 is in-.

circuited by a switch 19. Connectedto the two opposite central poles of switch 20,.is a

' circuit comprising a source of energy, such as a battery 21, a resistor 22 and an ductors ,26. A conductor 27 is'connected to a point between lamps24 and 25 and to the central opposite polev of switch 20, a battery 28 being inserted in the circuit.

The movable armature 7 .is energized through a. circuit containing battery 29,,re sistor 30, and ammeter 31.

In operating my magnetic testing apparatus, a standard drill 14, for instance, 1s inserted in the apparatus and clamped by screws 16, the current flowing through the movable armature7having been previously 1 adjusted, and switch -being closed in the upper position. A flux is thus producedin the magnetic circuit, as shown by the arrows, Fig. 3, and causes la'mp to light and pointer 8 to be deflected to the right. 10'

An unknown drill 15 is then inserted in the opposite end of the apparatus and is secured in place.

If the unknown drill is weaker magneti cally than the standard drill, the deflection of pointer 8 on scale 9 will be to the right. Since the right-hand lam 25 is lighted and the pointer 8 deflects to t e right, the reading is arbitrarily considered as minus, indicating that the drill being tested has less permeability than the standard drill. Switch 20 is opened and the reading then taken, indicatin the difference of remanent magnetism 0 the samples. Switch 19 is then opened and switch 20 is closed in the lower position, resistor 18 having first been ad- ]usted so that the coercive force exerted on standard drill 14 is suflicient to reduce its magnetism to zero. In this position of the apparatus, lamp 24 is lighted and, if the deflection of pointer 8 is to the left, the indication oi" the unknown sample is minus.

The procedure is now repeated several times to obtain several readings which are averaged to give a mean set of values. The three points obtained in this test, namely the difference in maximum permeability, remanent ma etism, and coercive force are usually sufiicient to give a very good indication of the ph sical characteristics of a material. If a stan ard drill, which is known to have the desired physical properties, is used, an apparatus such as described enables the user to determine very readily whether or not the unknown drills are of the correct chemical composition and have received the proper heat treatment.

My new apparatus has many advantages over apparatus hitherto used or suggested for testing of materials of this kind. The apparatus is very sensitive, since the movable armature may be adjusted to give large defiections with small fluxes because differences in fluxes are noted instead of the actual fluxes produced with any one sample in the circuit. The apparatus is very accurate in that there are no compensatin coils, and leakage effects are balanced. ince the results are stated in terms of a standard, it is unnecessary to periodically calibrate the instrument.

I claim as my invention:

1. A testing apparatus comprising a plurality of magnetic yokes, means for allowing the insertion of articles to be tested between said yokes, pole pieces formed centrally thereon, a movable armature between said pole pieces, and coils between the outer ends of said yokes.

2. A testing apparatus comprising a plurality of magnetic yokes, pole pieces formed centrally thereon, a movable armature between said pole pieces, coils between the outer ends of said yokes, and alined openings in said coils and yokes for allowing the insertion of articles to be tested.

3. A testing apparatus comprising a plurality of magnetic yokes, pole pieces formed centrally thereon, an armature between said pole pieces, coils between the outer ends of said yokes, alined openings in said coils and yokes for allowing the insertion of articles to be tested, and means for securing said articles therein.

In testimony whereof, I have hereunto subscribed my name this 18th day of October 1921.

THOMAS SPOON ER. 

